The viruses and microorganisms present in the nose, throat, and respiratory tract are aerosolized during dental procedures
"The fluids in the mouth are grossly contaminated with bacteria and viruses. Dental plaque, both supragingival and in the periodontal pocket, is a major source of these organisms. It should not, however, be overlooked that the mouth also is part of the oronasal pharynx. As part of this complex, the mouth harbors bacteria and viruses from the nose, throat and respiratory tract. These may included various pathogenic viruses and bacteria that are present in the saliva and oral fluids. Any dental procedure that has the potential to aerosolize saliva will cause airborne contamination with organisms from some or all of these sources."
Harrel SK, Molinari J. Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc. 2004 Apr;135(4):429-37. doi: 10.14219/jada.archive.2004.0207. PMID: 15127864; PMCID: PMC7093851.
High concentrations of live SARS-CoV-2 virus is consistently detected in the saliva of COVID-19 positive patients
"A total of 12 patients with laboratory-confirmed 2019-nCoV infection in Hong Kong were included. The median age was 62.5 years, ranging from 37 to 75 years. There were 5 female and 7 male patients. At the time of writing, all patients were still hospitalized. Saliva specimens were collected at a median of 2 days after hospitalization (range, 0–7 days) (Figure 1).The 2019-nCoV was detected in the initial saliva specimens of 11 patients (91.7%). For patient K, the first saliva specimen collected on the day of hospital admission tested negative. The median viral load of the first available saliva specimens was 3.3 × 10^6 copies/mL (range, 9.9 × 10^2 to 1.2 × 10^8 copies/mL)."
Kelvin Kai-Wang To, Owen Tak-Yin Tsang, Cyril Chik-Yan Yip, Kwok-Hung Chan, Tak-Chiu Wu, Jacky Man-Chun Chan, Wai-Shing Leung, Thomas Shiu-Hong Chik, Chris Yau-Chung Choi, Darshana H Kandamby, David Christopher Lung, Anthony Raymond Tam, Rosana Wing-Shan Poon, Agnes Yim-Fong Fung, Ivan Fan-Ngai Hung, Vincent Chi-Chung Cheng, Jasper Fuk-Woo Chan, Kwok-Yung Yuen, Consistent Detection of 2019 Novel Coronavirus in Saliva,Â Clinical Infectious Diseases, Volume 71, Issue 15, 1 August 2020, Pages 841â€“843,Â https://doi.org/10.1093/cid/ciaa149
HEPA filtration and air recirculation has been shown to be extremely effective in many sensitive medical spaces
"The combination of HEPA filtration and air recirculation has been shown to be extremely effective in many space functions such as ORs, AIIRs, and PEs. These systems clean air by simultaneously removing (i.e., filtering) and diluting (through recirculation) contaminants from the space. They have shown significant reduction in the number of bacterial colonies, and surrogate particulate matters previous studies, and they are expected to show a similar efficiency for the COVID-19 pandemic. The role of air distribution systems in buildings during an outbreak has been the subject of previous research. A finding that is worthy of reiteration is from Streifel and colleagues (1995) that showed HEPA filters are remarkably efficient in capturing submicron particles. The SARS-CoV-2 virus is shown to have a diameter less than 1 μm. This further suggests that HEPA filters will be effective tools to mitigate hospital spread, as noted in a recent review on the potential airborne route of the SARS-CoV-2 transmission in hospitals."
Mousavi ES, Kananizadeh N, Martinello RA, Sherman JD. COVID-19 Outbreak and Hospital Air Quality: A Systematic Review of Evidence on Air Filtration and Recirculation [published online ahead of print, 2020 Sep 11]. Environ Sci Technol. 2020;acs.est.0c03247. doi:10.1021/acs.est.0c03247